Showing papers by "Sushil Adhikari published in 2014"

Effects of Temperature and Equivalence Ratio on Pine Syngas Primary Gases and Contaminants in a Bench-Scale Fluidized Bed Gasifier

Abstract: Effects of equivalence ratio (ER = 0.15, 0.25, and 0.35 at 934 °C) and temperature (790, 934, and 1078 °C at 0.25 ER) were investigated in air gasification of pine for primary gases and contaminants. CO and H2 increased while CO2 and CH4 decreased from 790 to 1078 °C. Opposite trends were observed for ER. Based on overall contaminant weight, tar was highest at all temperatures (7.81, 8.24, and 8.93 g/kg dry biomass) and ERs (13.08, 8.24, and 2.51 g/kg dry biomass). NH3 varied from 1.63 to 1.00 g/kg dry biomass between 790 and 1078 °C and from 1.76 to 1.47 g/kg dry biomass between 0.15 and 0.35 ER. H2S ranged between 0.13 and 0.17 g/kg dry biomass from 790 to 1078 °C and between 0.154 and 0.18 g/kg dry biomass from 0.15 to 0.35 ER. Finally, HCl yields ranged from 13.63 to 0 mg/kg dry biomass and from 11.51 to 0.28 mg/kg dry biomass over the range of temperature and ER, respectively.

Catalytic pyrolysis of raw and thermally treated cellulose using different acidic zeolites.

Abstract: Fast pyrolysis of biomass using zeolite catalyst has shown to be effective in improving aromatic production This study focuses on aromatic production through catalytic pyrolysis of major biomass constituent ie, cellulose Furthermore, cellulose was torrefied to understand torrefaction’s effect on pyrolysis products The influence of SiO2/Al2O3 ratios of zeolite (ZSM-5) catalyst on aromatic production during pyrolysis of raw and torrefied cellulose was investigated Results showed that the catalyst acidity played a pivotal role in eliminating anhydro sugars and other oxygenated compounds while producing more aromatics The maximum aromatic yield (~25 wt%) was obtained when ZSM-5 with the highest acidity (SiO2/Al2O3 = 30) was used, while the lowest yield (799 wt%) was obtained when the least acidic catalyst was used (SiO2/Al2O3 = 280) for raw cellulose pyrolysis Torrefaction process showed to have positive effect on the aromatic production from pyrolysis There were no aromatics produced from pyrolysis of raw cellulose in the absence of catalyst, whereas significant amount of aromatic compounds were produced from both catalytic and noncatalytic pyrolyses of torrefied cellulose The aromatic hydrocarbons produced from catalytic pyrolysis of torrefied cellulose were 5 % more than those produced from raw cellulose at the highest temperature and catalyst acidity (SiO2/Al2O3 = 30)

Inhibitory activity of carbonyl compounds on alcoholic fermentation by Saccharomyces cerevisiae.

Abstract: Aldehydes and acids play important roles in the fermentation inhibition of biomass hydrolysates. A series of carbonyl compounds (vanillin, syringaldehyde, 4-hydroxybenzaldehyde, pyrogallol aldehyde, and o-phthalaldehyde) were used to examine the quantitative structure-inhibitory activity relationship of carbonyl compounds on alcoholic fermentation, based on the glucose consumption rate and the final ethanol yield. It was observed that pyrogallol aldehyde and o-phthalaldehyde (5.0 mM) reduced the initial glucose consumption rate by 60 and 89%, respectively, and also decreased the final ethanol yield by 60 and 99%, respectively. Correlating the molecular descriptors to inhibition efficiency in yeast fermentation revealed a strong relationship between the energy of the lowest unoccupied molecular orbital (ELUMO) of aldehydes and their inhibitory efficiency in fermentation. On the other hand, vanillin, syringaldehyde, and 4-hydroxybenzaldehyde (5.0 mM) increased the final ethanol yields by 11, 4, and 1%, respectively. Addition of vanillin appeared to favor ethanol formation over glycerol formation and decreased the glycerol yield in yeast fermentation. Furthermore, alcohol dehydrogenase (ADH) activity dropped significantly from 3.85 to 2.72, 1.83, 0.46, and 0.11 U/mg at 6 h of fermentation at vanillin concentrations of 0, 2.5, 5.0, 10.0, and 25.0 mM correspondingly. In addition, fermentation inhibition by acetic acid and benzoic acid was pH-dependent. Addition of acetate, benzoate, and potassium chloride increased the glucose consumption rate, likely because the salts enhanced membrane permeability, thus increasing glucose consumption.